Method of producing substrate having a particulate metallic coating

ABSTRACT

A method of producing a substrate having a particulate coating of high surface area to mass ratio, said method comprising in sequence the steps of: I. disposing particles between a substrate and an intermediate body wherein the particles are harder than the substrate; and the intermediate body is softer than the particles but is harder than the substrate; II. compressing the substrate and intermediate body, with particles therebetween whereby the intermediate body pushes the particles into the substrate; and III. removing the intermediate body from the particles leaving them embedded in the substrate. The coating substrates produced by the process of the present invention find utility as catalytic devices to accelerate or retard chemical reactions, as getter devices to sorb residual gases in closed vessels such as electronic tubes, and with further processing as capacitors.

Unite ttes Ptent llllelllla Port/a et a1. Mar. 2%, 19972 541 MEETHtJ D@1 1 PRQD UCING SUBSTRATE 3,549,357 12/1970 Osborne ..117/31 x MAW/ENG AIPARFHCUH'ATE METALLHQ FOREIGN PATENTS OR APPLICATIONS @UATENG 5,77412/1915 Great Britain ..117/31 1721 P911110 61W; 198 085 6/19670.5.5.12. ..117/31 11111-111110 lflndl; Marlo Zucclhlnelll, all ofM1131" [my Primary Examiner-John F. Campbell [73] Assignee: SAJES.Getter-s S. p.A., Milan, Italy Assistant Examiner D0flald 3 3Att0mey-Burns, Doane, Benedict, Swecker and Mathis [22] Filed: May 11,1970 211 Appl. No.: 33,794 [57] ABSTRACT A method of producing asubstrate having a particulate coat- W A P WWRPM ing of high surfacearea to mass ratio, said method comprising [63] Continuation-impart ofSer. No. 527,906, Feb. 16, in Sequence the Steps of:

1966, abandoned.

I. disposing particles between a substrate and an inter- [52] US. (11....117/22, 117/31, 117/130 R, mediate body wherein the particles areharder than th 3 117/160 29/1912 29/420 29/423, 29/527-7 substrate; andthe intermediate body is softer than the r zg/DIG- 264/111 252/181-7particles but is harder than the substrate: [51;] 1113111. C11 ..B'Il5b7/l, B44c 1/06, 1344C 1/08 [L compressing the Substrate and intermediatebody with [51 lFnelld ntfieareh ..29/191.2,420, 423, 527.7, particlestherebetween whereby the intermediate body 29/D1G. 32; 264/111; 117/100M, 31, 130 R, 22, ushes the particles into the substrate; and

160 R; 252/181] [11. removing the intermediate body from the particlesleaving them embedded in the substrate. [56] lReEerences Cited UNITEDSTATES PATENTS The coating substrates produced by the process of thepresent invention find utility as catalytic devices to accelerate or re-2,373,405 4/1945 Lowlt ..29/420 tat-d Chemical reactions as getterdevices to Sorb residual 2-626458 1/1953 gases in closed vessels such aselectronic tubes, and with 3,002,834- 10/1961 D1 Pasquale ..29/420 UX fth processing as capacitors 3,093,501 6/1963 Clayton ..117/31 X3,152,892 10/1964 Clark ..29/420 UX 16 Claims, 4 Drawing FiguresPATENTEU MAR 2 8 I972 lNVENToRs PAOLO dELLA PORTA TIZIANO A. GIORGIBRUNO KINDL MARIO ZUCCHINELLI PATENTEDmza 1972 3.652.317

sum 2 or 2 2-i- 2O B IFFI IP QQM L 'IIIIII l FIG.4

INVENTORS PAOLO dELLA PORTA TIZIANO A- GIORGI BRUNO KINDL MARIOZUCCHINELLI Mlli'lilillfillill @IF FERGIDIUCIING SUBSTRATE HAVWG AFAIRTHUJLATE METALLIIC COATING CROSS rdEFERENCE TO RELATED APPLICATIONSThis application is a continuation-in-part of US. application Ser. No.527,906 filed Feb. 16, 1966, now abandoned, the disclosure of which isincorporated herein by reference.

Processes for producing substrates having thereon a particulate metalliccoating are notoriously well known in the art. However, most priorprocesses require the use of a binder to hold the metal particles to thesubstrate. In an effort to avoid the use of a binder it has beensuggested to place the metal particles on the substrate to be coated andthen pass these between the nip or rotating rolls to embed the particlesin the surface of the substrate. However, such processes suffer from anumber of disadvantages. One disadvantage is the wear of the rolls whichis especially acute when the metal particles are hard. This wear of therolls necessitates their frequent replacement with a concurrent expense.However, an even more troublesome effect of the wear of the rolls istheir inability to exert an even pressure on the particles with theresult that only portion of the substrate is coated or alternatively anuneven coating results. Another disadvantage of the use of rolls incontact with metal particles is that the action of the rolls on theparticles substantially reduces their total surface area. Thisespecially troublesome when the desired coated substrate is onepreferably having a high surface area to mass ratio of the coatingparticles.

lvlarly of the prior processes require the use of superambienttemperatures increasing expense and the necessity for elaboratecontrols. Many other prior processes do not produce a coated substratehaving physical characteristics rendering it suitable for the intendeduse. Examples of such physical characteristics include among others ahigh heat transfer coefficient between the metal particles and thesubstrate, a resistance of the coated substrate to mechanical shocks, toultrasonic vibrations, and to thermally induced stresses such as arecaused by heating the coated substrate to high temperatures such asthose of 1,000 C. and higher. Many of these coated substrates lackfreedom from loose particles which may be created by separationofparticles of the metallic coating from the substrate.

Because of the above described disadvantages such processes have beenfound unsuitable for the production of getter devices, catalyticdevices, and capacitors.

it is therefore an object of the present invention to provide animproved method for producing a substrate having a particulate metalliccoating thereon which method is substantially free of one or more of thedisadvantages ofprior methods.

Another object is to provide an improved method which does not requirethe use ofa binder.

a further object is to provide an improved method which can be practicedat ambient temperatures.

A still further object is to provide an improved method employing rollwhich are not subject to wear.

i another object is to provide an improved method for producing a coatedsubstrate such as those suitable to be used a catalytic devices, getterdevices, or capacitors.

"till another object is to provide an improved method for producing acoated substrate which has the above described desirable physicalcharacteristics.

Still another object is to provide a method for producing an improvedgetter device having a high surface area to mass ratio the getter metaland which is free of loose particles.

A tiitional objects and advantages of the present invention wili beapparent to those skilled in the art by reference to the detaileddescription thereof and drawings wherein: itt t is a cross-sectionalview with an enlargement of about 300 diameters of a coated substrateproduced by the method of the present invention wherein the coating hasa thickness approximately equal to one particle diameter and;

lFlG. is a cross-sectional view with an enlargement of about 300diameters of a coated substrate produced by the method of the presentinvention wherein the particulate metallic coating has a thickness ofapproximately 3 particle diameters, this figure being a drawingcorresponding to a microphotograph representing the structure takenalong line 2-2 of FIG. d and;

FIG. 3 is a cross-sectional view with an enlargement of about 1,300diameters of a coated substrate produced by the method of the presentinvention wherein the original substrate comprised a hard base having asofter metallic coating thereon and;

FIG. 4 is a schematic representation of an apparatus suitable forpracticing the method of the present invention.

In accordance with the present invention there is provided a method ofproducing a substrate having a particulate metallic coating of highsurface area to mass ratio and usually greater than 2 cm."'/mg. Themethod comprises in sequence the steps of: r

I. disposing metal particles between a substrate and an intermediatebody wherein the particles are harder than the substrate; and theintermediate body is softer than the particles but is harder than thesubstrate;

II. compressing the substrate an intermediate body, with particlestherebetween whereby the intermediate body pushes the particles into thesubstrate; and

III. removing the intermediate body from the particles leaving themembedded in the substrate.

Referring now to the drawings and in particular to FIG. ll there isshown a substrate 1 of stainless steel having an upper coating 2 and alower coating 3 comprising metal particles of a zirconium alloypartially embedded in the surface of the substrate 1. FIG. 2 shows aniron substrate i having coatings 5 and 6 wherein these coatings 5 and 6have a total thickness which is approximately equal to three times thediameter of a single particle. As can be seen the metal particles incontact with the substrate 4 are partially embedded therein whereas theother particles are attached to one another or held in place by smallcold microwelds (not shown) between the individual particles. FIG. 3discloses a base 7 of iron having aluminum thereon which actually formsthe substrate 8. The particles forming the coating 9 are partiallyembedded in this substrate 8.

Referring now to FIG. 4 there is shown an apparatus it) suitable forpracticing the process of the present invention. in the practice of thisprocess loose metal particles ii and R2 are disposed respectivelybetween a substrate 13 and an upper intermediate body 14 and thesubstrate 13 and a lower intermediate body 15. Most conveniently themetal particles ii are placed on the substrate 13 whereas the metalparticles M are placed on the lower intermediate body 15 to form acomposite structure which is passed between the nip of two rolls i6 and17 rotating respectively in the direction of arrows l8 and 19. Theapparatus 10 is provided with means for maintaining the distance betweenthe rolls less than the combined thickness of the substrate 13,particles Ill and 17., and intermediate bodies 14 and I5. In thepreferred embodiment wherein the intermediate bodies 14 and 15 arework-hardenable the rolls id and 17 press the intermediate bodies lidand 15 with a force such that the intermediate bodies M and 15 undergoplastic deformation with concurrent work-hardening while effectivelypushing the metal particles ii and 112 into the substrate 33 withoutsubstantially reducing the total surface area of the metal particles illand 12.

The entire composite structure then leaves the nip between rolls i6 and17 with the intermediate bodies M and i5 adlrering to the metalparticles Ill and 12 which are embedded in the substrate 13 and arewelded to one another by cold microwelds. The intermediate bodies l4 andE5 are then removed leaving behind the coated substrate 26]. By virtueof the above described relationship in hardness between the metalparticles 11 and 12, the substrate l3 and the intermediate bodies Ml and15 the metal particles 11 and i2 adhere substantially completely to thesubstrate 13 rather than to the intermediate bodies M and 15. Thisrelationship in hardness is critical to the successful practice of themethod of the present invention. For example, if the intermediate bodies14 and 115 are of the same hardness as the substrate R3 the particles lland i2 will be randomly embedded in the substrate 113 and theintermediate bodies lid and 115. On the other hand if the substrate if)is harder than the intermediate bodies l4 and 15 the particles willpreferentially embed themselves into the intermediate bodies M and iii.if the particles ii and 12 are softer than either the intermediatebodies 114 and 15 or the substrate i3 they will be plastically deformedlosing their surface area and will not become embedded in the substrate113.

The metal particles can be of widely varying particle sizes but aregenerally those which pass through a US. standard screen of 10 mesh perinch and are preferably those which pass through a US. standard screenof 100 mesh per inch and are retained on a screen of 600 mesh per inch.

Broad and preferred ranges of Vickers hardness for the intermediatebody, the metallic particles and the substrate are given in thefollowing table:

Vickers Hardness Component Broad Preferred Example Range Range (kg/mm)g/mm) (kg/mm) intermediate body l-60O 10il-300 180 Particles l00=c200-800 400 Substrate l-400 10-200 90 The values given in this table arenon-limiting in the sense that specific values within the above rangesmust be chosen while maintaining the herein-described hardnessrelationship. in a preferred embodiment of the present invention theintermediate body has a Vickers hardness at least 50 and preferably atleast 100 kgjmm. less than the particles; and the substrate has aVickers hardness of at least lll and preferably at least ill) kgJmm.less than the intermediate body.

The particles of the metal to be embedded in the substrate are chosenwith respect to the desired end use of the product. Thus if a getterdevice is desired particles of a non-evaporable getter metal areemployed whereas if a catalytic device is desired particles of acatalyst metal are chosen. Finally if a capacitor is desired metallicparticles are employed which are electrically conductive in the broadestaspect any prior known non-evaporable getter metal can be employed inthe production of getter devices. Examples of suitable getter metalsinclude among others zirconium, titanium, tantalum, niobium, vanadiummixtures thereof and alloys thereof with one another and with othermetals which do not materially reduce the gas sorptive capacity of thesegetter metals. The preferre getter metal is an alloy of to 30 andpreferably 13 to 13 weight percent aluminum balance Zirconium. When itis desired to produce catalytic devices the metal particles are thosewhich have heretofore been found to catalyze the particular chemicalreaction. Examples of suitable catalytic rials include among othersplatinum, zirconium, vanadium, tantalum. Examples of electricallyconductive particles suitable for producing capacitors include amongothers iron, silver, copper and preferably aluminum.

The substrate and the intermediate bodies can be of any metal which hasthe herein described hardness relationship. Examples of suitable metalsinclude among others soft iron, steel, and stainless steel. it must beemphasized that the chemical nature of the elements making up the alloysemplayed as substrates and intermediate bodies is not critical. in factit is conceivable that alloys of identical chemical composition can beemployed as both provided that they have differing hadnesses. As isapparent to those skilled in the art differing resses can be imparted byconventional metallurgical techniques such as heat treatment, coldrolling and the like.

The invention is further illustrated by the following examples in whichall parts and percentages are by weight unless otherwise indicated.These non-limiting examples are illustrative of certain embodimentsdesigned to teach those skilled in the art how to practice the inventionand to represent the best mode contemplated for carrying out theinvention.

XAMPLE 1 This example illustrates the method of the present inventionwherein the resulting structure is a getter device.

Referring to H6. 4 finely divided particles of a nonevaporable getteralloy available from SAES Setters S.p.A. as St llllll is placed on aniron substrate 0.0M) inches thick. The St 101 is an alloy of 16 percentaluminum, balance zirconium and passes through a screen of mesh per inchand is retained on a screen of 600 mesh per inch. The particles of St101 in their sheet form exhibit a Vickers hardness of 400 kg./mm. Thesubstrate has a Vickers hardness of 90 kg./mm. A single intermediatebody of iron having a Vickers hardness of 180 kg./mm. and a thickness of0.010 inches is placed on top of the metal particles and the resultantcomposite passed between the nip of two rotating rolls. The intermediatebody is then removed leaving the particles embedded in the substrate.

XAMPLE 2 This example illustrates the process of the present inventionwherein the resultant product is a catalytic device.

The procedure of Example l is repeated except that the particles of St101 are replaced with platinum and the substrate is replaced with one ofaluminum having a Vickers hardness of 50 kg/mm. and the intermediatebody is replaced by one of iron having a Vickers hardness of kg./mm. Theresultant.

catalytic device functions satisfactorily to increase the reaction rateof a chemical reaction.

Although the invention has been described in considerable detail withreference to certain preferred embodiments thereof, it will beunderstood that variations and modifications can be effected within thespirit and scope of the invention as described above and as defined inthe appended claims.

We claim:

ll. A mechanical method of producing a metallic substrate having ametallic particulate coating of high surface area to mass ratio, saidmethod comprising in sequence the steps of:

l. disposing metallic particles between the metallic substrate and anintermediate body wherein the particles are harder than the substrate;and the intermediate body is softer than the particles but is harderthan the substrate;

ll. employing a compressing means in order to compress the substrate andintermediate body, with particles therebetween whereby the intermediatebody pushes the particles into the substrate; and

ill. removing the intermediate body from the particles leaving themembedded in the substrate.

2. The process of claim ll wherein the particles are placed on thesubstrate, and wherein an additional amount of particles are placed on asecond intermediate body which is on the side of the substrate oppositethe first intermediate body in order to produce a structure havingparticles embedded on both sides of the substrate.

3. The process of claim ll wherein the particles are susceptible to coldwelding to one another and to the substrate.

The process of claim 1 wherein the particles are of a size such thatthey pass through a US. standard screen of 10 mesh per inch.

5. The process of claim l wherein the substrate has a Vickers hardnessof 10 to 200 kg./mm.

6. The process of claim 11 wherein the intermediate body has a Vickershardness of l00 to 300 kgJmmF.

7. The process of claim l wherein the metallic particles have a Vickershardness of 200 to 800 lrg/mmf.

ii. The process of claim it wherein the intermediate body has a Vickershardness at least 50 kg./mrn. less than the particles.

9. The process of claim it wherein the substrate has a Vickers hardnessat least 40 kg./mrn. less than the intermediate body.

lib. A mechanical method of producing a structure of high area havingparticles of metal embedded in a metallic substrate, said methodcomprising in sequence the steps of:

l. disposing loose particles of metal between the metallic substrate anda work hardenable intermediate body wherein the particles are harderthan the substrate; and the intermediate body is softer than theparticles but is harder than the substrate;

passing the substrate and intermediate body, with loose particlestherebetween, between the nip of two rotating rolls wherein the distancebetween the rolls in less than the combined thickness of the substratethe intermediate body and the mass of loose particles; whereby theintermediate body undergoes plastic deformation with the concurrent workhardening while effectively pushing the particles into the substratewithout substantially reducing V the total surface area of theparticles; and V V, V, 7

ill. removing the intermediate body from the particles leaving thempartially embedded in the substrate.

The process of claim ll wherein the distance between the surnames of therolls is suiiiciently small that the intermediate body and the substrateboth exhibit plastic deformation, but is not so small as tosubstantially reduce the total surface area of the particulate material.

A mechanical method of producing a getter device having r articles of anon-evaporable getter metal embedded in a me allic substrate, saidmethod comprising in sequence the step oi":

disposing particles of a non-evaporable getter metal between themetallic substrate and an intermediate body wherein the particles areharder than the substrate and the intermediate body is softer than theparticles but is harder than the substrate;

ll. passing the substrate and intermediate body, with particlestherebetween, between the nip of two rotating rolls whereby theintermediate body pushes the particles into the substrate; and

ill. removing the intermediate body from the particles leaving themembedded in the substrate.

113. The process of claim 12 wherein the non-evaporable getter materialis a zirconium-aluminum alloy.

The process of claim i3 wherein the zirconium-aluminum alloy contains to30 weight percent aluminum balance zirconium.

15. A mechanical method of producing a getter device having particles ofa non-evaporable getter metal embedded in a metallic substrate, saidmethod comprising in sequence the steps of:

l. disposing loose particles of a non-evaporable getter metal betweenthe metallic substrate and an intermediate body wherein the particlesare harder than the substrate and the intermediate body is softer thanthe particles but is harder than the substrate and is in awork-hardenable condition;

ll. passing the substrate and intermediate body, with loose particlestherebetween, between the nip of two rotating rolls wherein the distancebetween the rolls is less than the thickness of the substrate andintermediate body with loose particles therebetween; whereby theintermediate body undergoes plastic deformation with concurrent workhardening while effectively pushing the particles into the substratewithout substantially reducing their surface area; and

Ill. removing the intermediate body from the particles leaving thempartially embedded in the substrate.

16. A mechanical method of producing a getter device having particles ofa non-evaporable getter metal embedded in a metallic substrate, saidmethod comprising in sequence the steps of:

l. disposing loose particles of a non-evaporable getter metal consistingessentially of an alloy of 13 to 18 weight percent aluminum balancezirconium between the substrate and a work hardenable intermediate bodywherein the intermediate body has a Vrckers hardness at least 100 kgjmm.less than the particles and the metallic substrate has a Vickershardness at least kg/mm less than the intermediate body;

ll. passing the substrate and intermediate body, with loose particlestherebetween, between the nip of two rotating rolls wherein the distancebetween the rolls is less than the thickness of the substrate andintermediate body with loose particles therebetween; whereby theintermediate body undergoes plastic deformation with concurrent workhardening while effectively pushing the particles into the substratewithout substantially reducing their surfaces arca; and

Ill. removing the intermediate body from the particles leaving thempartially embedded in the substrate.

*srerrn

2. The process of claim 1 wherein the particles are placed on thesubstrate, and wherein an additional amount of particles are placed on asecond intermediate body which is on the side of the substrate oppositethe first intermediate body in order to produce a structure havingparticles embedded on both sides of the substrate.
 3. The process ofclaim 1 wherein the particles are susceptible to cold welding to oneanother and to the substrate.
 4. The process of claim 1 wherein theparticles are of a size such that they pass through a U.S. standardscreen of 10 mesh per inch.
 5. The process of claim 1 wherein thesubstrate has a Vickers hardness of 10 to 200 kg./mm.2.
 6. The processof claim 1 wherein the intermediate body has a Vickers hardness of 100to 300 kg./mm.2.
 7. The process of claim 1 wherein the metallicparticles have a Vickers hardness of 200 to 800 kg./mm.2.
 8. The processof claim 1 wherein the intermediate body has a Vickers hardness at least50 kg./mm.2 less than the particles.
 9. The process of claim 1 whereinthe substrate has a Vickers hardness at least 40 kg./mm.2 less than theintermediate body.
 10. A mechanical method of producing a structure ofhigh surface area having particles of metal embedded in a metallicsubstrate, said method comprising in sequence the steps of: I. disposingloose particles of metal between the metallic substrate and a workhardenable intermediate body wherein the particles are harder than thesubstrate; and the intermediate body is softer than the particles but isharder than the substrate; II. passing the substrate and intermediatebody, with loose particles therebetween, between the nip of two rotatingrolls wherein the distance between the rolls in less than the combinedthickness of the substrate the intermediate body and the mass of looseparticles; whereby the intermediate body undergoes plastic deformationwith the concurrent work hardening while effectively pushing theparticles into the substrate without substantially reducing the totalsurface area of the particles; and III. removing the intermediate bodyfrom the particles leaving them partially embedded in the substrate. 11.The process of claim 1 wherein the distance between the surfaces of therolls is sufficiently small that the intermediate body and the substrateboth exhibit plastic deformation, but is not so small as tosubstantially reduce the total surface area of the particulate material.12. A mechanical method of producing a getter device having particles ofa non-evaporable getter metal embedded in a metallic substrate, saidmethod comprising in sequeNce the steps of: I. disposing particles of anon-evaporable getter metal between the metallic substrate and anintermediate body wherein the particles are harder than the substrateand the intermediate body is softer than the particles but is harderthan the substrate; II. passing the substrate and intermediate body,with particles therebetween, between the nip of two rotating rollswhereby the intermediate body pushes the particles into the substrate;and III. removing the intermediate body from the particles leaving themembedded in the substrate.
 13. The process of claim 12 wherein thenon-evaporable getter material is a zirconium-aluminum alloy.
 14. Theprocess of claim 13 wherein the zirconium-aluminum alloy contains 5 to30 weight percent aluminum balance zirconium.
 15. A mechanical method ofproducing a getter device having particles of a non-evaporable gettermetal embedded in a metallic substrate, said method comprising insequence the steps of: I. disposing loose particles of a non-evaporablegetter metal between the metallic substrate and an intermediate bodywherein the particles are harder than the substrate and the intermediatebody is softer than the particles but is harder than the substrate andis in a work-hardenable condition; II. passing the substrate andintermediate body, with loose particles therebetween, between the nip oftwo rotating rolls wherein the distance between the rolls is less thanthe thickness of the substrate and intermediate body with looseparticles therebetween; whereby the intermediate body undergoes plasticdeformation with concurrent work hardening while effectively pushing theparticles into the substrate without substantially reducing theirsurface area; and III. removing the intermediate body from the particlesleaving them partially embedded in the substrate.
 16. A mechanicalmethod of producing a getter device having particles of a non-evaporablegetter metal embedded in a metallic substrate, said method comprising insequence the steps of: I. disposing loose particles of a non-evaporablegetter metal consisting essentially of an alloy of 13 to 18 weightpercent aluminum balance zirconium between the substrate and a workhardenable intermediate body wherein the intermediate body has a Vickershardness at least 100 kg./mm.2 less than the particles and the metallicsubstrate has a Vickers hardness at least 80 kg./mm.2 less than theintermediate body; II. passing the substrate and intermediate body, withloose particles therebetween, between the nip of two rotating rollswherein the distance between the rolls is less than the thickness of thesubstrate and intermediate body with loose particles therebetween;whereby the intermediate body undergoes plastic deformation withconcurrent work hardening while effectively pushing the particles intothe substrate without substantially reducing their surface area; andIII. removing the intermediate body from the particles leaving thempartially embedded in the substrate.